I encountered an issue today that resulted in different sized objects after resizing same sized objects due to an issue with the move selection tool. Note in the below examples there is a second black box under the first on a different layer to show its original vs its new size. If you create an initial selection: Then resize the selection using the Move Selection Tool: Then, using the move pixels tool, move the square to the right. Finally, while holding shift (to maintain the ratio), drag a corner slightly: You'll notice the resize seems to use the original selection's ratio (in picture 1) rather than the edited selection's ratio (in picture 2) causing the image to loose its ratio. This is particularly notable in this example, but if you are getting the selection close to perfect, then editing the selection to be exact, then resizing it you may not notice it resulting in slight ratio changes. Note: if you need a workaround for this if you cut and paste the selection it now uses the new ratio.